KX, A QUANTITATIVELY MINOR PROTEIN FROM HUMAN ERYTHROCYTES, IS PALMITOYLATED IN-VIVO

Kx is a quantitatively minor blood group protein of human erythrocytes which is thought to be a membrane transporter. In the red cell membra ne, Kx forms a complex stabilized by a disulfide bond with the Kell bl ood group membrane protein which might function as a metalloprotease. The palmitoylation status of these proteins was studied by incubating red cells with [H-3] palmitic acid. Purification of the Kell-Kx comple x, by immunochromatography on an immobilized human monoclonal antibody of Kell blood group specificity demonstrated that the Kx but not the Kell protein is palmitoylated. Six cysteines in Kx are predicted to be intracytoplasmic and might be targets for palmitoylation. Three of th ese cysteines are present in a portion of sequence which is predicted to form an amphipathic alpha helix. Palmitoylation of one or several o f these cysteines might contribute to anchor the cytoplasmic portion o f the Kx protein to the inner surface of red cell membrane. (C) 1998 A cademic Press.